The NHS could be "in peril" if the government's plans to overhaul it are derailed by doctors and nurses' organisations, a group of GPs piloting the reforms has warned.

The health secretary, Andrew Lansley, has proposed that the management of hospitals and budgets in England is reformed by allowing doctors rather than managers to control health services and budgets.

The British Medical Association, the Royal College of Nurses and the Royal College of Midwives oppose the reform, describing it as a covert privatisation of the NHS. David Cameron agreed to "pause" the reforms last year as a result of the opposition.

But more than 50 doctors who are already managing health services through clinical commissioning groups (CCGs), have backed the government's reforms, saying the professional bodies did not represent their views.

"Blanket opposition to the NHS reforms by the British Medical Association and the Royal College of Nurses is not representative of the views of GPs … and nurses who support us," they said in a letter.

The doctors wrote that CCGs were already improving services in the areas of England in which they are established.

"The risks of derailing the development of clinical commissioning must not be underestimated," they wrote. "Without strong clinical leadership and the co-ordinated efforts of local clinicians, the NHS itself may be in peril – local services can only be improved if we all pull together."